Field of the Invention
This invention relates to a torque transmission apparatus having a vibration damping function.
Description of the Related Art
As a torque converter having a lock-up mechanism, for example, an apparatus having vibration damping function is known, in order to prevent torsional vibration due to engine rotational fluctuation from transmitting directly to a transmission during operation of the lock-up mechanism. Among apparatuses of this type, the apparatus described in Japanese Examined Patent Publication No. 5051447 (JP5051447B) has a first elastic member, a main mass body and a second elastic member serially connected and interposed between a lock-up clutch and turbine runner. In addition, a dynamic damper is formed by connecting an auxiliary mass body to the main mass body through a third elastic member.
The auxiliary mass body of an apparatus described in JP5051447B is projected in the axial direction so as to be rotatable relative to the main mass body, and the third elastic member is installed between a cover plate which is fixed on the auxiliary mass body is fixed and a housing hole formed in the main mass body. Therefore, the apparatus becomes large in the axial direction, so that the apparatus is difficult to mount in situations subject to heavy layout restrictions.